Multistage fluidized bed reactor



Nov. 3, 1959 A. A. JONKE ETAL 2,

MULTISTAGE FLUIDIZED BED REACTOR 2 Sheets-Sheet 1 Filed April 18, 1957 IN VENTORS fllbeft fl Jo/zke Johan Gfdcle y Norman MLe-wttz 1959 A. A. JONKE EIAL 2,911,290

MULTISTAGE FLUIDIZED BED REACTOR 2 Sheets-Sheet 2 Filed April 18, 1957 United States Patent A, 2,911,29 MULTISTAGE FLUIDIZED BED REACTOR 7 Application April 18, 1957, Serial No. 653,722

2 Claims. 01. 2s 2s4 This invention relates to a reactor of the type in which a chemical reaction takes place between a granular solid that flows in one direction through the reactor and a gas that flows in the opposite direction through the solid so as to fluidize the same. More specifically, the reactor is one of the multistage type. I

It is known to conve1tUO to U0 by the use of H and to convert U0 to UF by use of HF, and both of these reactions can be carried out in the reactor of the present invention.

When reactions of this type are carried out through the counter current flow of a granular solid and a fluidizing gas, some difliculties are encountered with the use of several stages in the reactor. It has been found that the granular solid will flow down from one stage to the other even when the flow of fiuidizing gas stops. This is obviously undesirable, because it means that the solid goes through the reactor without the desired chemical reaction.

In accordance with the present invention, the various stages of the reactors are provided with baifles that permit the upward flow of fluidizing gas through a granular solid and yet prevent or limit the downward flow of the solid when the flow of the gas is shut off.

In the drawings:

Fig. 1 is a vertical sectional view of a first form of reactor of the present invention;

Fig. 2 is a horizontal sectional view taken on the line 22 of Fig. 1 and showing the relationship of perforations in a plate to perforations in a baflle therebelow;

Fig. 3 is a vertical sectional view of a second form of reactor of the present invention;

Fig. 4 is a horizontal sectional view taken on the line 44 of Fig. 3 and showing the relationship of perforations in a plate to perforations in a baflle;

Fig. 5 is a vertical sectional view taken on the line 5-5 of Fig. 4; and

Fig. 6 is a vertical sectional view of a third form of reactor of the present invention.

The reactor of Fig. 1 comprises a vertical column 10, a plurality of plates 11 constituting stages, a plurality of baffies 12, and a plurality of downcomer pipes 13. The column is circular and cylindrical and has a vent 14 for gas at the top, a feed inlet 15 near the top, a product outlet 16 at the bottom, and a gas inlet 17 at the bottom.

There are three plates or stages 11, and, as shown in Fig. 2, each plate has a plurality of perforations 18. One of the baffles 12 is supported by and just below each plate 11 in spaced relation thereto and has a plurality of perforation 12 which are olfset from the perforations 18 in the associate-d plate 11 and are larger in diameter than these perforations 18. The plates 11 fit the interior of the column 10. The baflies 12 are smaller in diameter than the plate 11 so as to be spaced from the interior of the column 10, with the result that the space between each baifie 12 and its associated plate 11 can be completely cleared of solid material when necessary. There are two downcomer pipes 13 extending through ice 2 and supported by the upper and intermediate sets of plate 11 and baflle 12, one pipe 13 being at one side of the column 10, and the other at the other side of the column. The product outlet 16 extends through the lower set of plate 11 and baffle 12 much in the manner of the downcomer pipes 13.

A granular solid such as U0 or U0 enters the column 10 through'the feed inlet 15, and fluidizing gas such as H or HF enters the column 10 through the gas inlet 17. U0 in granular form may be produced by the process disclosed in Lawroski et al. application, Serial No. 658,901, filed May 13, 1957. The upward flow of gas through a given bafile 12 and associated plate 11 prevents the downward fiow of solid therethrough and compels the level solid to rise until overflow takes place in the associated downcomer pipe 13, which brings the solid to the plate 11 below. The movement of the gas through the solid fluidizes it and causes it to behave somewhat like a boiling liquid. The movement of the gas through the solid facilitates the chemical reaction between the solid and the gas. For the conversion of U0 to U0 a temperature of 575 C. and a slightly superatmospheric pressure may be used, and N is added to the,I-I if needed to provide suflicient fluidization. For the conversion of U0 to UF a temperature of 450 C. and a slightly superatmospheric pressure may be used, N is added to the HF if needed to provide sufficient fluidizationand H is added to prevent any oxidation of the uranium and to complete reduction of U0; to U0 The reactor of Fig. 1 may be formed of stainless steel.

The unaligned perforations 18 and 19 in the plates 11 and baflles 12 permit the upward flow of the fluidizing gas theret'hrough, but will not permit the solid material to flow through the bafiles 12 when the introduction of fluidizing gas to the reactor is stopped. Small cones of solid material are formed below each perforation 18, in the plates 11 in the manner shown in Fig. 5 for the reactorsof Fig. 4, these cones preventing the further flow of solid material when the flow of gas is stopped. When the flow of gas is resumed, it will pass through the perforations 19 in each baffle 12, clearing out the' accumulations of solid material directly below the perforations 18 in the associated plate 11. To prevent accidental blocking of the narrow spaces between the plates 11 and baffies 12, special gas nozzles 20 are provided to blow these spaces clean, either at the discretion of the operator or at controlled intervals. The fluidized solid material does not flow through the plates 11 and baffles 12, but instead, fiows from a given stage to the stage below through the appropriate downcomer pipe 13 when the level of fluidized material at the given stage becomes high enough for the material to overflow into the downcomer pipe.

This reactor was operated successfully without difficulties in two 13-hour runs in the conversion of U0 to UF The reactor of Fig. 3 comprises a vertical column 21, a plurality of plates22 constituting stages, a plurality of battles 23, and a plurality of weirs 24 which with certain wall portions of the column 21 constitute downcomer pipes. The column 21 is cylindrical and oblong in horizontal section, i.e., the shorter horizontal dimension being perpendicular to the plane of the paper in Fig. 3. The column 21 has a vent 25 for gas at the top, a feed inlet 26 at the top, a product outlet 27 at the bottom, a gas inlet 28 at the bottom below the bottom plate 22 and baffie 23, and a gas inlet 29 near the bottom of the column below the next-to-the-bottom plate 22 and baflle 23.

There are four plates or stages 22, and, as shown in Fig. 4, each plate is oblong and has a plurality of perforations 30, which, as shown in Fig. 5, have upper conical portions and lower cylindrical portions. Perforations 30 with their conical upper portions produce an improved gas distribution and a better contact between gas and solids. Each plate 22"ex tend s btv'veefi' warrant aiid back walls of the column ZIIand from a side wall thereof atevin .av free endatwhichftheiassoc I I s :7 I cured. ,Each weir '2 extends between the fIoiitQandback walls of the mums 21 so that d ncomer pipejor means'isfform'edby the'weir 2.4, the 'fron v I 1 of the column, and the side wall bf thefco n nlbppos'ite that vfrom which the associatedplat 22; L i plates .22 extend alternately froni oppos ite e's ofj the p H e of eaehiplate 22 in spaced relation theretofand has .a praisiityjof perforations 311', which, as sh in.Eig."4,, are oifset from theperforations 30 in the te I in'jdiameter than theupper portions oflthe' perforations 3D and larger in A dia'meter'ftha'h the lower portions 1 theresfyfaaea baffle z3' i sfsinaller'in outline than'the associated plate 22 so as tobespacedf from .the associated weir 2.4,.t'he front and backwalls ofthe column'jl," and the side wall thereof from which the as sdciatedplate 22 extends, with the resultithatfl SpaCe betwee'n"eachbafile 23 55a its "associated plate 122' can he completely cleared of solid material 'when necessary.

' The partsof the reactor .ofFig. 3 may be formed of stainless. steel. i p i i The operation of the reactor of Fig. 3 is much like that of thereactor of Fig. '1. Fluidizing gas enters the column 21.throu'gh'the two inlets 28 and 29, so that the how of g'asi's uniform across the entire width of the column. The two' inlets 28 and 29 are desirable, because eachplate 22 extends only part way across the column 21. Previous mention has been made with reference to the reactor of Fig. 1, of the factthat, as shown in Fig. 5, small cones of'solid material'are formed below perforations 30 inthe plates22 when the How of gas is stopped, these cones preventing thefurther flow of solid material. The reactor of Fig. 6 comprises averticalcolumn 32, anilliirality of openrended inverted cones 33 constituting the bafiles 23 issupported by and just below 22. and are smaller.

stages; a plurality of baffies 34, and apluralityiofldowncorner pipes 35. The column 32 is circular andcylindrical and has a vent 36 for gas" at thevtop. a feed inlet 37 at thetop, a product outlet 38at the bottom, a gas inlet 39 at the bottom. "Izher'e are three cones 33 each. having a single perforation' formed by its open 'small lower end. The downcomerpipes 35 have restrictions 3% inith eir-lower ends andare slecuredto .thecones 33 so as to be supported thereby and extend through'th e cones offset pa riallel relation to the axes thereof. Restrictions 39a prevent thefluidizinggas from causing blow back of the solid in the'downcorners, so that a more even flow of solid ma; terial from stage to stage results. The bottom downcomer pipe 35 extends into the product outlet 38. ffhe downcomer pipes 35 are alternately adjacent opposite s i des of o'f'tlie column 32. One of the two baffles 34 is secured to each of the uppertwo downcomer pipes 35 so as to be located just below the associated cone in spaced relation thereto. Each of the bafiles 3.4 has a weep hole 41) which is aligned with axes of the associated cone 33 and is small'enthan the open lowenend of the cone.

.4. Around each baffle 34 a weir 41 extends frorn. and back to the associated downcomer pipe 35. Each bafiie 34 to a point somewhat below the top of the downcomer pipe 35 below. Below the bottom cone 33 is a floor 43 which serves as a baffle and is imperforate except at the region through which the bottom downcomer pipe 35 extends. The floor 43 is sp a'eedfrom a bottom 44 ofthe column Sal-from. which the product Olitlfit 38 extends.

The operatipn ofthe reactor of Fig-6 islike thaLof the reactor of Fi-gfll' -The ..'gfanu la'r solid 'ahdith'e l'flui diii n'g a s i u h.th i!i1 y n kin e 39,, e sst ve y. and the gas "and product resulting from the .chemicalfreaction exit through the yent 36 and outlet 38, respectively. In the event 'ofl'os'sbf a bed oro'ther operational difi'iculty, the flow of fluid izing gas canybe stopped, permitting the granular solid to flow downward in the fill pipes 42, filling all beds the desired levels. The beds are filled to the ,desired levels, ,since thelower ends ,of the fill pipe 42 ,aifehelow thetop of the ,d ricorner pipes 35 below. W h fl w fi i i asets sh te oi anua solidlhelhot toni oi: le"t 3 3.ont o the 43 b elow is limitedjto the .fbrrna lonj fof a cone of granular material below the siren end gofthe eoneli@as in Fig. 5 for the .reactor of Fig. 4. W 0

scope ofthe appended claims.

' W hat is fclai ined ist eneas flui iz d:. 9 ,Q .-9Q1. 2R fi n fi-Wl? t t e P l t films rn ta i s a e d sp s d across the column, each stage comprising anopemended P s -9 mi1 er t t n in t stas han u '3 6 st g s. 1 b i .1 9 heated i s 219W th apex q l'the ra l th s qqistfed tag aplut it e l we r extending arg ed eac vbefiil a lu a t 52 e ong t tubes, one extending down from the hole in each baffle, siwn sms .P p x en n .thrw h h one i fis relationto the axes thereof, rneans forjntroducing fluidis a i the -ettsz 9 th William r n t l izin e a 41. 499 Qfi-Ih lwmnta ed inlet n the .191 o -.tb qll m aadlam oduc qutle't nea th l Q tQtt of ,th tn- 2. The reactor specified in claim l,..th e downcomer p n -.12 .la etqd lteinate adiacem n s of t 9 mm andtheath s d st tea es Gt efl in the l ihi pa .PN IEP .i TV-AI.E PATE T 

1. A MULTISTAGE FLUIDIZED-BED REACTOR COMPRISING A VERTICAL CYLINDRICAL COLUMN, A PLURALITY OF STAGES DISPOSED ACROSS THE COLUMN, EACH STAGE COMPRISING AN OPEN-ENDED INVERTED CONE FORMING A PERFORATION IN THE STAGE, A PLURALITY OF BAFFLES LOCATED JUST BELOW THE STAGES, EACH BAFFLE HAVING A SMALL HOLE LOCATED JUST BELOW THE APEX OF THE CONE OF THE ASSOCIATED STAGE, A PLURALITY OF LOW WEIRS, ONE EXTENDING AROUND EACH BAFFLE, A PLURALITY OF ELONGATED TUBES, ONE EXTENDING THROUGH THE CONES IN OFFSET DOWNCOMER PIPES EXTENDING THROUGH THE CONES IN OFFSET RELATION TO THE AXES THEREOF, MEANDS FOR INTRODUCING FLUIDIZING GAS IN THE BOTTOM OF THE COLUMN, A VENT FOR THE FLUIDIZING GAS AT THE TOP OF THE COLUMN, A FEED INLET NEAR THE TOP OF THE COLUMN, AND A PRODUCT OUTLET NEAR THE BOTTOM OF THE COLUMN. 